Can you quickly predict whether a man will be a tough negotiator?

So, okay, you’re negotiating a price and would like to know how aggressive you can be. It would be helpful to know the other guy’s testosterone level, right? You might be able to get a clue just by looking at his ring finger.

Look for a wedding ring. Studies show that married men have lower testosterone levels than single men.

Check out how long the ring finger is relative to the index finger. The ratio of the ring finger to the index finger is determined by prenatal exposure to the androgen that determines gender. A number of recent studies have reported that men with long ring fingers (relative to the index) excel at competitive sports and deal making, and are more likely to reject low offers in the ultimatum game. A Cambridge University group headed by John Coates examined financial traders and found correlations between ring-to-index-finger ratio and trading success, and also between testosterone levels and trading success.

As a tentative rule, you may have the best luck driving a hard bargain with a man whose ring finger is short (compared to the index) and has a wedding ring on it.